1. Technical Field
The present disclosure relates to a liquid pump and a Rankine cycle device including the liquid pump.
2. Description of the Related Art
Lately, energy systems using natural energy, such as sunlight, or exhaust heat of various kinds are attracting attention. One example of such energy systems is a system employing the Rankine cycle. Generally, in a system employing the Rankine cycle, an expander is operated with high-temperature, high-pressure working fluid, and extracts power from the working fluid to generate electric power. The high-temperature, high-pressure working fluid is generated by a pump and a heat source (such as solar heat, geothermal heat, or exhaust heat from a car).
As illustrated in FIG. 9, Japanese Unexamined Patent Application Publication No. 2012-202374 describes an electric generating device 300. The electric generating device 300 includes a circulation flow path 306, which includes a pump 301, an evaporator 302, an expander 303, and a condenser 304. The expander 303 expands a working medium evaporated by the evaporator 302 and extracts kinetic energy from the working medium. An electric generator 305 is connected to the expander 303 and is driven by the expander 303. The working medium in a liquid state is condensed and pressurized to a predetermined pressure by the pump 301 and is discharged to the evaporator 302.
The circulation flow path 306 between the condenser 304 and the pump 301 is provided with a pressure sensor 311 and a temperature sensor 312. The pressure sensor 311 detects a pressure Ps of the working medium on the inlet side of the pump 301. The temperature sensor 312 detects a temperature Ts of the working medium on the inlet side of the pump 301. The saturation vapor pressure of the working medium at the inlet of the pump 301 is derived from the detected value of the temperature sensor 312. On the basis of the saturation vapor pressure thus derived and the pressure of the working medium detected by the pressure sensor 311, the difference (difference in pressure) between the pressures is obtained, and the output of the pump 301 is adjusted according to the difference in pressure. In this way, the occurrence of cavitation in the pump 301 can be prevented.
As illustrated in FIG. 10, Japanese Unexamined Patent Application Publication No. 2004-346820 describes a refrigerant pump 500. The refrigerant pump 500 includes a hermetic case 510, an electric motor 511, a pump mechanism 512, a drive shaft 513, a suction board 516, a suction pipe 521, and a discharge pipe 520. The electric motor 511 includes a stator 511a and a rotor 511b. The stator 511a is attached to the outside of the hermetic case 510, and the rotor 511b is disposed in the hermetic case 510. Near the inlet of the suction pipe 521 of the suction board 516, a cutout 519 is formed by cutting out part of the suction board 516. In this way, a refrigerant suction path is securely obtained.